Zinc base die casting alloy



Patented Oct. 10, 1933 PATENT? OFFICE 1,930,341 zmc BASE on: CASTING ALLOY John B. Freeman, Jr., Waterbury, Conn., as-

signor to The American Brass Company, Waterbury, Conn., a corporation of Connecticut No Drawing. Application August 29, 1931 Serial No. 560,227

2 Claims.

This invention relates to zinc base die casting alloys and has for its object a new and improved alloy for die castings.

Heretofore the design of die casting machines 5 has been such that the mechanism is to a great extent completely immersed in themolten alloy to be cast. The casting mechanism is of necessity made of steel and cast iron both of which are attacked by molten zinc and zinc base alloys with the exception of zinc alloys containing more than 0.25% aluminum, the presence of which greatly reduces the attack of the steel and iron.

parts by the zinc. Aluminum has thus heretofore been an essential requirement in die casting alloys.

There have recently become available die casting machines in which the melting chamber is separated from the casting mechanism. As a result it is possible to economically die cast products of zinc base alloy which do not contain aluminum.

In the preparation of such products zinc of commercial quality has been used such as zinc of quality defined as No. 1 or high grade by the American Society for Testing Materials in their specification No. 36-18. High grade zinc of this quality may contain as much as 0.07% lead and cadium respectively and 0.03% of iron.

Zinc base alloys containing from about 0.5 to about of copper prepared from high grade zinc as above specified are open to the objection that the alloys develop what is commonly termed hot shortness in the die casting process more particularly in the manufacture of the more intricate castings.

I have discovered'that this hot shortness" when present in alloys of zinc-and copper is due to the presence of impurities, more particularly lead and cadium, usually found in high grade 40 zinc as above specified. I have discovered however, that .by reducing the impurity content of zinc base copper alloys, in particular the lead and cadmium content, castings of the above alloys may be produced which are free from the 0 objection of hot shortness and therefore are suitable for a wide range of applications where the alloys previously discussed prepared from high grade zinc containing normal impurities are not suitable.

Based on this discovery my invention resides in the provision of a new zinc base die casting alloy containing approximately 0.50 to 15% of copper and balance zinc metal of special purity such that the resultant'alloy is free from ele- 7 ments that cause hot shortness, in particular the elements lead and cadmium. More'particularly the invention involves the provision of a new zinc base die casting alloy containing from about 0.5% to 15% of copper in which the zinc base is 75 of zinc metal containing total impurities not to exceed 0.02%. The above range of about 0.50% to 15% copper produces a series of useful alloys, but the preferred range is from about 2% to a about 6% copper and the balance zinc.

Having thus set forth the nature of my invention, what I claim is:

1. As a new article of manufacturea metallic product comprising a die casting made of a zinc base alloy containing from about 0.5 percent to 5 about 15 percent copper and the remainder zinc metal containing 99.98 percent or more zinc.

2. As a new article of manufacture a metallic product comprising a die casting made of a zinc base alloy containing from about 2 percent to about 6 percent copper and the remainder zinc metal containing at least 99.98 percent zinc. I

JOHN. R. FREEMAN, JR. 

